Angel, I'm so glad you have an appointment. I think the nurse's suggestion to go to the ER in the hospital where this doctor practices is a good one. Can you do that soon? At least then you would get an xray of your knee. If it's something really serious, you might get referred to the doctor faster than July 23. I want to be sure that you don't injure yourself more by waiting.
Right now don't even think about what may have happened and who is to blame. It really doesn't matter. The important thing is to get to a good surgeon who can help get you back on track.